AU2021101821A4 - A process to digest the gibbsite bauxite containing boehmite - Google Patents
A process to digest the gibbsite bauxite containing boehmite Download PDFInfo
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- AU2021101821A4 AU2021101821A4 AU2021101821A AU2021101821A AU2021101821A4 AU 2021101821 A4 AU2021101821 A4 AU 2021101821A4 AU 2021101821 A AU2021101821 A AU 2021101821A AU 2021101821 A AU2021101821 A AU 2021101821A AU 2021101821 A4 AU2021101821 A4 AU 2021101821A4
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- digestion
- bauxite
- gibbsite
- calcium
- containing boehmite
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
- C01F7/06—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process
- C01F7/062—Digestion
- C01F7/0633—Digestion characterised by the use of additives
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
- C22B3/12—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic alkaline solutions
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
- C01F7/06—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process
- C01F7/0613—Pretreatment of the minerals, e.g. grinding
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B21/00—Obtaining aluminium
- C22B21/0015—Obtaining aluminium by wet processes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Inorganic Chemistry (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Environmental & Geological Engineering (AREA)
- Metallurgy (AREA)
- Manufacturing & Machinery (AREA)
- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Nutrition Science (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The technology of the short time digestion at the moderate-temperatures for the gibbsite bauxite
containing boehmite is provided by this invention for reducing the high caustic and bauxite
consumption in the traditional Bayer digestion process. The invention adopts one stage
grinding process with a closed circuit by the optimized grinding process parameters and steel
ball ratios for the more uniform solid size slurry of -15 mesh (-1mm). The digestion temperature
is selected in a range of 225-250°C and the digestion time is shortened to 3-30 minutes. The
calcium compound additive with an equivalent lime addition of 1-3% is added for the better
digestion efficiency. In this digestion process the sodium oxide to silica ratio (ratio of Na20 to
SiO2 , same as below) in the bauxite residue after digestion will be reduced to about 0.4, and
the alumina to silica ratio (ratio of A1 20 3 to SiO 2 , same as below) in the bauxite residue can
reach about 0.85, owing to which the caustic and bauxite consumption can be significantly
reduced. This invention breaks through the bottlenecks of high bauxite and caustic
consumption in the traditional Bayer digestion process both at low temperatures and high
temperatures so that it has a broad industrial application prospect. This innovation is especially
suitable for gibbsite bauxite containing boehmite with high content of nonreactive silica
minerals.
1/1
FIGURES
Gibbsite bauxite containing boehmite
I \
_ One-stage closed circuit grinding Calcium containing additives
Solid size<1 mm
Short time digestion at moderate temperatures
Bauxite residue Sodium aluminate
with low A/S solution (which can
and N/S be used to produce
alumina)
Figure 1
Description
1/1
Gibbsite bauxite containing boehmite
One-stage closed circuit grinding Calcium containing additives _
Solid size<1 mm
Short time digestion at moderate temperatures
Bauxite residue Sodium aluminate with low A/S solution (which can and N/S be used to produce alumina)
Figure 1
A process to digest the gibbsite bauxite containing boehmite
This invention belongs to the technical field of alumina production and particularly
relates to Bayer digestion technology of the gibbsite bauxite containing boehmite.
Bayer process is widely used to treat different types of bauxite to produce alumina. The
core technology in Bayer process is bauxite digestion, in which the alumina minerals in
the bauxite are digested into the caustic liquor ( called "spent liquor" in the industry) so
that the alumina content in the liquor becomes higher (called "pregnant liquor"), while
the other impurity minerals, such as silica, iron and titanium minerals in the bauxite will
react with liquor or other additives. These reaction products from the impurity minerals
will be clarified from sodium aluminate liquor (pregnant liquor) and enter residues in the
form of insoluble compounds (called "red mud" in alumina refineries). Alumina is
produced from the pregnant liquor after filtration, seed precipitation and calcination.
In Bayer process, bauxite digestion is the most important production process, where most
alumina minerals, such as gibbsite and boehmite will react with caustic liquor to produce
sodium aluminate solution, while the silica minerals such as kaolinite and quartz will be
desilicated to form insoluble hydrated sodium aluminosilicates into the red mud. The
digestion technology is particularly important for these reactions because different
digestion processes will directly affect the digestion efficiency of the alumina minerals,
and also affect the desilication performance and reaction rate of silica minerals.
Traditional Bayer digestion technology includes low temperature digestion process and
high temperature digestion process. In the low-temperature digestion process the bauxite is usually digested at about 145°C for more than 30 minutes, in which the gibbsite will be completely dissolved, while boehmite can hardly be digested. If this digestion technology is used to treat gibbsite bauxite containing boehmite, the bauxite digestion rate and recovery rate of alumina will be very low to lead to high bauxite consumption depending on the boehmite content in the bauxite.
For the high-temperature digestion process bauxite is generally digested at 255-280°C, in
which the gibbsite and boehmite are both digested, while almost all the silica minerals in
the bauxite will be reacted with liquor or additives to bring about loss of some dissolved
alumina and caustic soda.
In view of the above technical problems for Bayer digestion process of gibbsite bauxite
containing boehmite, the present invention provides a new digestion method so called
short time digestion at the moderate temperatures.
The key points of the digestion technology are: (1) Adopting one-stage grinding process
with a closed-circuit suitable for grinding gibbsite bauxite containing boehmite until the
solid particle size in the slurry is more uniform and all less than 15 meshes (-1mm); (2)
The digestion conditions are as follows: the digestion temperatures are set in the range of
250-225°C, the digestion retention time is kept in the range of 3-30 minutes and calcium
compound additives are added with the quantity equivalent to 1-3% of lime addition.
Under these conditions of digestion process, the alumina to silica ratio of the red mud
from gibbsite bauxite containing boehmite can reach about 0.85, and the sodium oxide to
silica ratio will be reduced to about 0.4.
For example, the low grade gibbsite bauxite containing boehmite with high silica content
(10%), low alumina content (52%) and low alumina to silica ratio (5.2) is treated by traditional high temperature digestion process at 280°C for 5 minutes. As the digestion results, the alumina to silica ratio of the bauxite residue after digestion will be 1.05 and the sodium oxide to silica ratio will be 0.53. Based on the digestion data the alumina digestion rate becomes only 79.8%, the bauxite consumption per ton of alumina is as high as 2.41 tons and the chemical caustic consumption is up to 165 kg.
However, if the short time digestion at the moderate temperatures of the present invention
is adopted, the ratio of alumina to silica in the bauxite residue will be reduced to 0.85 and
the sodium oxide to silica ratio will be reduced to 0.40 so that the digestion rate of
alumina will be improved to 83.7% (increased by 3.9%), the bauxite consumption per
tons of alumina will be reduced to 2.30 tons (reduced by 4.5%) and the chemical caustic
consumption will be 119kg (reduced by 27.8%).
For the Bayer process refinery with an annual output of 1 million tons of alumina to treat
the above-mentioned lower-grade gibbsite bauxite containing boehmite, the annual
bauxite consumption will be reduced by 110,000 tons and the caustic consumption will
be reduced by 46,000 tons if the digestion technology of the present invention is used in
stead of traditional high temperature digestion technology. As a result the annual
economic benefit will be achieved to more than 15 million US dollars.
This invention is especially suitable for the lower grade gibbsite bauxite containing
boehmite with higher content of nonreactive silica minerals.
The purpose of this invention is to provide a new short time digestion technology at the
moderate-temperatures to produce alumina from the gibbsite bauxite containing
boehmite, which can greatly reduce the sodium oxide to silica ratio and alumina to silicon ratio in the red mud from this kind of bauxite, thereby reducing the caustic and bauxite consumption in the alumina production and also reducing the energy consumption of
Bayer process compared with the traditional high temperature Bayer process.
The invention is realized by the following technical solution.
The Bayer digestion technology of gibbsite bauxite containing boehmite comprises such
process steps as bauxite grinding, additive addition, digestion, which is characterized in
the following content:
1) Grinding process of gibbsite bauxite containing boehmite: One-stage closed
circuit grinding mill is adopted, with the maximum steel ball diameter of 100-200 mm
and the ball loading amount of 15-35%. The solid content and circulation rate in the mill
is controlled. The grounded slurry with more uniform solid sizes and -15 mesh (-1mm) is
obtained after grinding, while the content of solid particles smaller than 320 mesh in the
slurry is less than 30%.
2) Calcium additives addition: the calcium containing compound is added into the
mill for preparing the slurry for digestion of the gibbsite bauxite containing boehmite,
wherein the calcium-containing compound can be one or more of calcium salt, lime or
lime milk (calcium hydroxide); The addition amount of calcium containing compounds is
equivalent to 1% -3% of lime (CaO) for total bauxite mass.
3) The short time digestion at the moderate temperatures for the gibbsite bauxite
containing boehmite: The digestion temperature is controlled in the range of 250~225°C
according to the current process and equipment situation. The digestion retention time
is kept in the range of 3 minutes to 30 minutes; The caustic concentration of the spent
liquor is in the range of 100 - 220 g/L.
A new digestion technology to treat the gibbsite bauxite containing boehmite is put
forward in this invention. Under the conditions mentioned above the alumina to silica
ratio of the obtained bauxite residue is reduced to about 0.85, and the sodium oxide to
silica ratio is reduced to about 0.4.
The digestion results show that the alumina in the gibbsite bauxite containing boehmite
has been completely dissolved, while most of the nonreactive silica minerals in the
bauxite have not reacted. Therefore, the purpose of reducing bauxite and caustic
consumption is achieved.
As the patent creatively adopts the moderate digestion temperatures lower than the
traditional high digestion temperatures, the effects to reduce digestion steam consumption
and saving energy can also be achieved.
In order to explain the technical solutions in the present invention more clearly, the
drawings for the description of the embodiments will be briefly introduced below.
Obviously, the drawings in the following description are only some embodiments of the
present invention and other drawings can also be obtained based on these drawings by the
ordinary people in the field without paying creative labor, in which: Figure 1 is the flow
diagram of the digestion process for the gibbsite bauxite containing boehmite provided by
the present invention.
The technical solutions in the embodiments of the invention will be described clearly and
completely in combination with the drawings in the embodiments of the invention.
Obviously, the described embodiments are only part of the embodiments of the invention,
not all of them.
Please refer to Fig. 1, which is the flow chart of the digestion method for the gibbsite
bauxite containing boehmite provided by the present invention.
[Example 1]
A gibbsite bauxite containing boehmite contained 55% alumina, in which was 8% of
boehmite. The content of silica was 7%, in which the nonreactive silica accounted for
about 40% in the total silica minerals. The short time digestion at the moderate
temperatures was implemented in an alumina refinery. The grinding granularity of the
bauxite slurry passed through 15-mesh sieve, in which the content of -320-mesh particles
was less than 25%. The caustic concentration (Na20) of the slurry was 180g/L and lime
was added into the bauxite slurry with an addition amount accounted for 2% of the
bauxite mass. The digestion temperature was controlled at 238°C and the retention time
was kept in 8 minutes.
The digestion results under the new digestion process are as follows: the alumina to silica
ratio of the digested red mud was 0.79 and the sodium oxide to silica ratio of the red mud
was only 0.38. It could be estimated based on the mentioned above that the bauxite
consumption was reduced by 3.7%, the chemical caustic consumption was reduced by
about 2 3 .1%, and the digestion energy consumption was reduced by about 0.5GJ/t A1 2 0 3 .
[Example 2]
A gibbsite bauxite containing boehmite contained 53% alumina, in which existed 6%
boehmite. The silica content in the bauxite was 9.5%, in which nonreactive silica
accounted for about 38% in the total silica minerals. The short time digestion at the moderate temperatures was used in an alumina refinery to treat the gibbsite bauxite containing boehmite. The grinding granularity in the slurry all passed through 15 mesh sieve, in which the content of -320 mesh particles was less than 28%. The digestion temperature was controlled at 245°C and the digestion retention time was kept in 5 minutes. Lime milk was added, which was equivalent to 1% of bauxite mass. And the digestion caustic concentration was 160 g/L.
The digestion results were as follows: The alumina to silica ratio of the digested red mud
reached to 0.82 and the sodium oxide to silica ratio of the digested residue was only 0.40.
Therefore, it can be estimated from mentioned above that the bauxite consumption was
reduced by 4.8 % compared with that of the traditional high temperature digestion
process, the chemical caustic consumption was reduced by about 27.8 %, and the
digestion energy consumption was reduced by about 0.5 GJ/t A1 2 0 3 due to .the lower
digestion temperature.
[Example 3]
A gibbsite bauxite containing boehmite contained 51% alumina, in which was 6%
boehmite. The silica content was 10%, in which nonreactive silica accounted for about
% in the total silica minerals. The short time digestion at the moderate temperatures
was carried out in an alumina refinery to treat the gibbsite bauxite containing boehmite.
The solid particles in the grounded slurry all passed through 15 mesh sieve, in which the
content of -320 mesh particles was less than 30%. The digestion temperature was
controlled at 235°C and the digestion retention time was kept in 15 minutes. Lime was
added accounting for 2.5% of bauxite mass and the caustic concentration was 190 g/L.
The digestion results were as follows: the alumina to silica ratio of the digested residue
reached to 0.88, and the sodium oxide to silica ratio in the digested residue reached to
0.42. It could be estimated from mentioned above that the bauxite consumption was
reduced by 4%, the chemical caustic consumption was reduced by about 24% and the
energy consumption was reduced by about 0.6 GJ/t A1 2 0 3
. The mentioned above is only an embodiment of the present invention, which does not
limit the patent scope of the present invention. Any equivalent structure or equivalent
flow transformation made by using the contents of the specification in the present
invention, or directly or indirectly applied to other related technical fields, are equally
included in the patent protection scope of the present invention.
Claims (3)
1) Grinding process of gibbsite bauxite containing boehmite: One-stage closed
circuit grinding mill is adopted, with the maximum steel ball diameter of 100-200 mm
and the ball loading amount of 15-35%. The solid content and circulation rate in the mill
is controlled. The grounded slurry with more uniform solid sizes and -15 mesh (-1mm) is
obtained after grinding, while the content of solid particles smaller than 320 mesh in the
slurry is less than 30%.
2) Calcium additives addition: the calcium containing compound is added into the
mill for preparing the slurry for digestion of the gibbsite bauxite containing boehmite,
wherein the calcium-containing compound can be one or more of calcium salt, lime or
lime milk (calcium hydroxide); The addition amount of calcium containing compounds is
equivalent to 1% -3% of lime (CaO) for total bauxite mass.
3) The short time digestion at the moderate temperatures for the gibbsite bauxite
containing boehmite: The digestion temperature is controlled in the range of 250~225°C
according to the current process and equipment situation. The digestion retention time
is kept in the range of 3 minutes to 30 minutes; The caustic concentration of the spent
liquor is in the range of 100 - 220 g/L.
FIGURES 1/1
Figure 1
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2021101821A AU2021101821A4 (en) | 2021-04-09 | 2021-04-09 | A process to digest the gibbsite bauxite containing boehmite |
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| AU2021101821A AU2021101821A4 (en) | 2021-04-09 | 2021-04-09 | A process to digest the gibbsite bauxite containing boehmite |
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| Publication Number | Publication Date |
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| AU2021101821A4 true AU2021101821A4 (en) | 2021-06-10 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116287767A (en) * | 2023-02-17 | 2023-06-23 | 贵港沃斯顿科技有限公司 | Method for improving dissolution rate of indissolvable bauxite |
-
2021
- 2021-04-09 AU AU2021101821A patent/AU2021101821A4/en not_active Ceased
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116287767A (en) * | 2023-02-17 | 2023-06-23 | 贵港沃斯顿科技有限公司 | Method for improving dissolution rate of indissolvable bauxite |
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